Simultaneous Immobilization of Lead and Atrazine in Contaminated Soils Using Dairy-Manure Biochar

TLDR

Biochar derived from waste biomass is increasingly viewed as a green, cost‑effective amendment for environmental remediation. This study aimed to evaluate whether dairy‑manure biochar can immobilize both lead and the pesticide atrazine in contaminated soils. The authors incubated dairy‑manure biochar at 0, 2.5, and 5 % w/w with contaminated soils for 210 days, comparing its performance to commercial activated carbon. Dairy‑manure biochar effectively immobilized both lead and atrazine—reducing Pb and atrazine by >57 % and >66 % in CaCl₂ extracts, 70–89 % and 53–77 % in TCLP leachates, and up to 79 % and 73 % uptake by earthworms—likely via phosphorus‑induced hydroxypyromorphite formation and atrazine adsorption, whereas activated carbon only immobilized atrazine.

Abstract

Biochar produced from waste biomass is increasingly being recognized as a green, cost-effective amendment for environmental remediation. This work was to determine the ability of biochar to immobilize heavy metal Pb and organic pesticide atrazine in contaminated soils. Biochar prepared from dairy manure was incubated with contaminated soils at rates of 0, 2.5, and 5.0% by weight for 210 d. A commercial activated carbon (AC) was included as a comparison. The AC was effective in immobilizing atrazine, but was ineffective for Pb. However, biochar was effective in immobilizing both atrazine and Pb and the effectiveness was enhanced with increasing incubation time and biochar rates. After 210 d, soils treated with the highest rate of 5.0% biochar showed more than 57% and 66% reduction in Pb and atrazine concentrations in 0.01 M CaCl2 extraction, respectively. Lead and atrazine concentrations in the toxicity characteristic leaching procedure solutions were reduced by 70–89% and 53–77%, respectively. Uptake of Pb and atrazine by earthworms (Eisenia fetida) was reduced by up to 79% and 73%. Phosphorus originally contained in biochar reacted with soil Pb to form insoluble hydroxypyromorphite Pb5(PO4)3(OH), as determined by X-ray diffraction, which was presumably responsible for soil Pb immobilization, whereas atrazine stabilization may result from its adsorption by biochar demonstrated by the significant exponential decrease of extractable atrazine with increasing organic C in biochar (r2 > 0.97, p < 0.05). The results highlighted the potential of dairy-manure biochar as a unique amendment for immobilization of both heavy metal and organic contaminants in cocontaminated soils.